Re: [PATCH bpf-next 09/18] bpf: Reject stack arguments if tail call reachable

bot+bpf-ci
2026-04-24T18:00:38Z

[-- Attachment #1: Type: text/plain, Size: 1674 bytes --]

> bpf: Reject stack arguments if tail call reachable
>
> Tailcalls have been deprecated. So reject stack arguments
> if tail call is in the way.

Multiple reviewers (bot+bpf-ci@kernel.org and sashiko-bot@kernel.org) raised
concerns across v4, v5, and v6 that the commit message inaccurately states
"Tailcalls have been deprecated" when the actual technical reason is that tail
calls and stack arguments require incompatible stack frame handling.

The author acknowledged this feedback in v5 but chose to keep the commit
message as-is, stating "Stack arguments and tail calls CAN work together.
However, since tail calls are in deprecation stage, it is not worthwhile to
involve stack arguments and tail calls together."

Could the commit message be more precise about the technical reason for this
restriction? Something along the lines of "tail calls and stack arguments
require incompatible stack frame handling" would better explain to future
readers why the combination is rejected, rather than relying on the
deprecation rationale.

Reference: https://lore.kernel.org/bpf/f163dcbf46e9511eba14b22ed10467984bda3bf07a3d1bd6cd27ae14eadc2056@mail.kernel.org/

> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c

[ ... ]

This commit fixes a bug but lacks a Fixes: tag. The suggested tag is:

Fixes: 8ade62ae1543 ("bpf: Support stack arguments for bpf functions")

---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

CI run summary: https://github.com/kernel-patches/bpf/actions/runs/24902767240